ALPR systems generally include various image processing and computer vision techniques for: (1) locating a license plate within a scene, (2) segmenting characters on the plate, and (3) performing optical character recognition to determine the character sequence.
In addition, determining the jurisdiction such as the state and plate type is often required. ALPR technologies can be utilized in, for example, electronic tolling, photo enforcement, parking, and other transportation applications where the vehicle identity is required. Performance requirements for ALPR systems are very high and are ever increasing in this competitive market space. Performance errors can be categorized into common failure modes. One prevalent failure mode is referred to as “confused characters”. Characters are confused with each other due to image noise. For example, “B” is often confused with “8” and “D” is often confused with “0” in the presence of image blur. In another common failure mode, the license plate frame partially covers the license plate obscuring character strokes such as making a “T” look like a “1” and an “E” look like a “F”. Other common failure modes and desired augmenting data are known a priori, as well.